There's no such thing as cheap blank DVDs or CDs. You either buy the cheapest with the understanding that they *will* get corrupted in 1-3 years and cost you extra time or loss, or you pay 1.5-3 times as much for quality media from a superior manufacturer like Taiyo Yuden with the understanding that they'll last longer.
But seriously, why buy crappy writable DVDs anyway, when you can get bigger, more reliable hard drives for just about 2x the price per GB? Yes, hard drives crash on occasion--but they don't routinely just go corrupt after a year. I have hard drives still working perfectly from 8 years ago. I don't have any writeable CDs that old, though my Taiyo Yudens from about 4 years ago are in good shape. Except for DVD-RAM (which was designed for professional, not just consumer, use), writable DVDs are even less proven to be reliable long-term.
Bottom line, unless you buy blank DVDs from top-quality manufacturing plants, expect them to die within several years. Brands don't usually list their manufacturing sources, and often source from several; but the very best always have the "Made in Japan" mark. Anything made anywhere else can be top-quality, or poor quality.